1. Field of the Invention
The present invention relates to a security fence employing a fiber optic cable attached to the security fence to monitor the integrity of the fence against intrusion or tampering. More particularly, the present invention relates to a device for inducing a stress into a fiber optic cable if a weight is placed upon the fiber optic cable or against the device itself.
2. Description of the Related Art
Security fences employing a fiber optic cable monitoring scheme are generally known in the background. For example, see applicant's prior application Ser. No. 10/713,425 filed Nov. 17, 2003, pending, entitled “APPARATUS AND METHOD TO DETECT AN INTRUSION POINT ALONG A SECURITY FENCE,” which is herein fully incorporated by reference. Also see applicant's prior application Ser. No. 10/842,545 filed May 11, 2004, pending, entitled “CLIPS FOR HOLDING FIBER OPTIC CABLES OF A SECURITY FENCE” which is herein fully incorporated by reference. Also see U.S. Pat. Nos. 4,275,294; 4,371,869; 4,399,430; 4,450,434; 4,558,308; 4,676,485; 4,680,573; 5,134,386; 5,416,467; 5,592,149; and the assignees' prior Korean Patents 1997-0009968, 20-0205489, and 20-0205490.
In the systems known in the background art, a length of fiber optic cable is formed into a pattern, such as a zigzagging pattern. The pattern is attached to an existing barrier type fence, such as a galvanized chain-link fence. The pattern in the fiber optic cable has a weave size and/or shape, which is smaller than the size of a human, so that a human cannot pass though the weave pattern without disrupting the fiber optic cable. In other words, a person would need to cut the fiber optic cable or severely distort the cable (e.g. by bending, stretching and/or pinching) to form a hole in the pattern large enough to pass through. Any such cutting or distortion of the fiber optic cable will interrupt or interfere with light passing through the fiber optic cable and will cause an alarm to be raised.
FIG. 1 illustrates a galvanized chain-link fence 10, in accordance with the background art. In FIG. 1, a fiber optic cable 12 is formed into a zigzagging pattern and attached to the barrier fence 10. A plurality of clips 14 hold the fiber optic cable in the zigzagging pattern. FIG. 2 is a close-up view of the zigzagging pattern of the fiber optic cable 12, with the barrier fence 10 removed for clarity.